package ru.space_game.resource;

import java.awt.Color;
import java.awt.Graphics;
import java.awt.Image;
import java.awt.color.ColorSpace;
import java.awt.image.BufferedImage;
import java.awt.image.ColorModel;
import java.awt.image.ComponentColorModel;
import java.awt.image.DataBuffer;
import java.awt.image.DataBufferByte;
import java.awt.image.Raster;
import java.awt.image.WritableRaster;
import java.io.IOException;
import java.net.URL;
import java.nio.ByteBuffer;
import java.nio.ByteOrder;
import java.nio.IntBuffer;
import java.util.HashMap;
import java.util.Hashtable;

import javax.swing.ImageIcon;

import org.lwjgl.BufferUtils;

import static org.lwjgl.opengl.GL11.*;

/**
 * A utility class to load textures for OpenGL. This source is based on a
 * texture that can be found in the Java Gaming (www.javagaming.org) Wiki. It
 * has been simplified slightly for explicit 2D graphics use.
 * 
 * OpenGL uses a particular image format. Since the images that are loaded from
 * disk may not match this format this manager introduces a intermediate image
 * which the source image is copied into. In turn, this image is used as source
 * for the OpenGL texture.
 * 
 * @author Kevin Glass
 * @author Brian Matzon
 */
public class TextureManager {
	/** The table of textures that have been loaded in this manager */
	private HashMap<String, Texture> table = new HashMap<String, Texture>();

	/** The colour model including alpha for the GL image */
	private ColorModel glAlphaColorModel;

	/** The colour model for the GL image */
	private ColorModel glColorModel;

	/** Scratch buffer for texture ID's */
	private IntBuffer textureIDBuffer = BufferUtils.createIntBuffer(1);

	private static final String TEXTURES_FOLDER = "resources/textures/";

	/**
	 * Create a new texture manager based on the game panel
	 */
	public TextureManager() {
		glAlphaColorModel = new ComponentColorModel(
				ColorSpace.getInstance(ColorSpace.CS_sRGB), new int[] { 8, 8,
						8, 8 }, true, false, ComponentColorModel.TRANSLUCENT,
				DataBuffer.TYPE_BYTE);

		glColorModel = new ComponentColorModel(
				ColorSpace.getInstance(ColorSpace.CS_sRGB), new int[] { 8, 8,
						8, 0 }, false, false, ComponentColorModel.OPAQUE,
				DataBuffer.TYPE_BYTE);
	}

	/**
	 * Create a new texture ID
	 * 
	 * @return A new texture ID
	 */
	private int createTextureID() {
		glGenTextures(textureIDBuffer);
		return textureIDBuffer.get(0);
	}

	/**
	 * Load a texture
	 * 
	 * @param resourceName
	 *            The location of the resource to load
	 * @return The loaded texture
	 * @throws IOException
	 *             Indicates a failure to access the resource
	 */
	public Texture getTexture(String resourceName) throws IOException {
		String path = TEXTURES_FOLDER + resourceName;
		Texture tex = table.get(path);

		if (tex != null) {
			return tex;
		}

		tex = getTexture(path, GL_TEXTURE_2D, // target
				GL_RGBA, // dst pixel format
				GL_LINEAR, // min filter (unused)
				GL_LINEAR);

		table.put(resourceName, tex);

		return tex;
	}

	/**
	 * Load a texture into OpenGL from a image reference on disk.
	 * 
	 * @param resourceName
	 *            The location of the resource to load
	 * @param target
	 *            The GL target to load the texture against
	 * @param dstPixelFormat
	 *            The pixel format of the screen
	 * @param minFilter
	 *            The minimizing filter
	 * @param magFilter
	 *            The magnification filter
	 * @return The loaded texture
	 * @throws IOException
	 *             Indicates a failure to access the resource
	 */
	public Texture getTexture(String resourceName, int target,
			int dstPixelFormat, int minFilter, int magFilter)
			throws IOException {
		int srcPixelFormat;

		// create the texture ID for this texture
		int textureID = createTextureID();
		Texture texture = new Texture(target, textureID);

		// bind this texture
		glBindTexture(target, textureID);

		BufferedImage bufferedImage = loadImage(resourceName);
		texture.setWidth(bufferedImage.getWidth());
		texture.setHeight(bufferedImage.getHeight());

		if (bufferedImage.getColorModel().hasAlpha()) {
			srcPixelFormat = GL_RGBA;
		} else {
			srcPixelFormat = GL_RGB;
		}

		// convert that image into a byte buffer of texture data
		ByteBuffer textureBuffer = convertImageData(bufferedImage, texture);

		if (target == GL_TEXTURE_2D) {
			glTexParameteri(target, GL_TEXTURE_MIN_FILTER, minFilter);
			glTexParameteri(target, GL_TEXTURE_MAG_FILTER, magFilter);
		}

		// produce a texture from the byte buffer
		glTexImage2D(target, 0, dstPixelFormat,
				get2Fold(bufferedImage.getWidth()),
				get2Fold(bufferedImage.getHeight()), 0, srcPixelFormat,
				GL_UNSIGNED_BYTE, textureBuffer);

		return texture;
	}

	/**
	 * Get the closest greater power of 2 to the fold number
	 * 
	 * @param fold
	 *            The target number
	 * @return The power of 2
	 */
	private static int get2Fold(int fold) {
		int ret = 2;
		while (ret < fold) {
			ret *= 2;
		}
		return ret;
	}

	/**
	 * Convert the buffered image to a texture
	 * 
	 * @param bufferedImage
	 *            The image to convert to a texture
	 * @param texture
	 *            The texture to store the data into
	 * @return A buffer containing the data
	 */
	@SuppressWarnings("rawtypes")
	private ByteBuffer convertImageData(BufferedImage bufferedImage,
			Texture texture) {
		ByteBuffer imageBuffer;
		WritableRaster raster;
		BufferedImage texImage;

		int texWidth = 2;
		int texHeight = 2;

		// find the closest power of 2 for the width and height
		// of the produced texture
		while (texWidth < bufferedImage.getWidth()) {
			texWidth *= 2;
		}
		while (texHeight < bufferedImage.getHeight()) {
			texHeight *= 2;
		}

		texture.setTextureHeight(texHeight);
		texture.setTextureWidth(texWidth);

		// create a raster that can be used by OpenGL as a source
		// for a texture
		if (bufferedImage.getColorModel().hasAlpha()) {
			raster = Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE,
					texWidth, texHeight, 4, null);
			texImage = new BufferedImage(glAlphaColorModel, raster, false,
					new Hashtable());
		} else {
			raster = Raster.createInterleavedRaster(DataBuffer.TYPE_BYTE,
					texWidth, texHeight, 3, null);
			texImage = new BufferedImage(glColorModel, raster, false,
					new Hashtable());
		}

		// copy the source image into the produced image
		Graphics g = texImage.getGraphics();
		g.setColor(new Color(0f, 0f, 0f, 0f));
		g.fillRect(0, 0, texWidth, texHeight);
		g.drawImage(bufferedImage, 0, 0, null);

		// build a byte buffer from the temporary image
		// that be used by OpenGL to produce a texture.
		byte[] data = ((DataBufferByte) texImage.getRaster().getDataBuffer())
				.getData();

		imageBuffer = ByteBuffer.allocateDirect(data.length);
		imageBuffer.order(ByteOrder.nativeOrder());
		imageBuffer.put(data, 0, data.length);
		imageBuffer.flip();

		return imageBuffer;
	}

	/**
	 * Load a given resource as a buffered image
	 * 
	 * @param ref
	 *            The location of the resource to load
	 * @return The loaded buffered image
	 * @throws IOException
	 *             Indicates a failure to find a resource
	 */
	private BufferedImage loadImage(String ref) throws IOException {
		URL url = TextureManager.class.getClassLoader().getResource(ref);

		if (url == null) {
			throw new IOException("Cannot find: " + ref);
		}

		// due to an issue with ImageIO and mixed signed code
		// we are now using good old fashioned ImageIcon to load
		// images and the paint it on top of a new BufferedImage
		Image img = new ImageIcon(url).getImage();
		BufferedImage bufferedImage = new BufferedImage(img.getWidth(null),
				img.getHeight(null), BufferedImage.TYPE_INT_ARGB);
		Graphics g = bufferedImage.getGraphics();
		g.drawImage(img, 0, 0, null);
		g.dispose();

		return bufferedImage;
	}
}